1. Field of the Invention
This invention relates generally to honeycomb structures and more particularly to honeycomb structures used for window coverings.
2. Description of the Prior Art
Various honeycomb structures are known in the art. For example, in U.S. Pat. No. 3,384,519 to Froget, a honeycomb structure is formed by joining a first material and a generally parallel second material with welded spaced-apart blades. In U.S. Pat. No. 4,861,404 to Neff, a honeycomb product is made in which two pleated sheets are connected by alternately extending legs.
In U.S. Pat. No. 4,685,986 to Anderson, a honeycomb structure is created in which the pleat ends of two sections of pleated material are adhered together. Alternatively, Anderson teaches adhering a bridge-like section of material to the opposite pleat ends.
In U.S. Pat. No. 4,974,656 to Judkins, several methods are shown for making honeycomb structures. One such method, shown in FIG. 5A involves adhering a span of material to each end of a pleat and a lift cord is disposed through a hole formed in the span material.
In any of the aforementioned honeycomb structures, a lift cord is incorporated into the structure when that structure is used as a window shade. It is the practice in the art to dispose the lift cords through the pleated material. Typically, holes are drilled into the pleated material through which the lift cords are disposed. It would be advantageous to locate these holes for the lift cords at the center of the honeycomb structure where the two pleated materials meet. For each of the prior art honeycomb structures noted above, the drilling or punching of the lift cord holes at this center location would be difficult due to the close cell nature of the final product as well as possible gumming of the drill by the applied adhesive.
Alignment problems could be incurred if one attempted to preform a lift cord hole in the pleats or on material spanning the pleats. When the lift cord holes are out of alignment, the lift cord will experience drag against the shade material.